package myLinkedList;

//ListNode代表一个节点
class ListNode{
    public int val;
    public ListNode next;

    public ListNode(int val){
        this.val = val;
    }
}

public class MyLinkedList {

    public ListNode head;//链表的头引用

    public void createList(){
        ListNode listNode1 = new ListNode(12);
        ListNode listNode2 = new ListNode(23);
        ListNode listNode3 = new ListNode(34);
        ListNode listNode4 = new ListNode(45);
        ListNode listNode5 = new ListNode(56);

        listNode1.next = listNode2;
        listNode2.next = listNode3;
        listNode3.next = listNode4;
        listNode4.next = listNode5;
        this.head = listNode1; //函数走完,局部变量都被回收,就剩下一个head
    }

    public void display(){
        ListNode cur = this.head;
        while (cur != null){
            System.out.print(cur.val +" ");
            cur = cur.next;
        }
        System.out.println();
    }

    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key){
        ListNode cur = this.head;
        while (cur != null){
            if (cur.val == key){
                return true;
            }
            cur = cur.next;
        }
        return false;
    };

    //得到单链表的长度
    public int size(){
        ListNode cur = this.head;
        int sum = 0;
        while (cur != null){
            sum++;
            cur = cur.next;
        }
        return sum;
    };

    //头插法
   public void addFirst(int data){
       ListNode node = new ListNode(data);
       node.next = this.head;
       this.head = node;
   };

   //尾插法
   public void addLast(int data){
       ListNode node = new ListNode(data);
       if (this.head == null){
           this.head = node;
       }else {
           ListNode cur = this.head;
           while (cur.next != null){
               cur = cur.next;
           }
           cur.next = node;
       }
   };

   //找到index-1位置的节点的地址
    public ListNode findIndex(int index){
        ListNode cur = this.head;
        while (index-1 != 0){
            cur = cur.next;
            index--;
        }
        return cur;
    }

   //任意位置插入,第一个数据节点为0号下标
   public void addIndex(int index,int data){
       if (index < 0 || index > size()){
           System.out.println("插入的位置不合法!");
           return ;
       }
       if (index == 0){
           addFirst(data);
           return;
       }
       if (index == size()){
           addLast(data);
           return;
       }
       ListNode cur =findIndex(index);
       ListNode node = new ListNode(data);
       node.next = cur.next;
       cur.next = node;
   };

    //找到要删除的关键字的前驱
    public ListNode searchPerv(int key){
        ListNode cur = this.head;
        while (cur.next != null){
            if (cur.next.val == key){
                return cur;
            }
            cur = cur.next;
        }
        return null;
    }

   //删除第一次出现关键字为key的节点
   public void remove(int key){
       if (this.head == null){
           System.out.println("单链表为空,不能删除!");
           return;
       }
       if (this.head.val == key){
           this.head = this.head.next;
           return;
       }

      //我最开始的写法,有点冗余,后面进行改进,遂加入searchPerv()简化
      /* ListNode cur = this.head;
       while (cur.next != null){
           if (cur.next.val == key){
               ListNode del = cur.next;
               cur.next = del.next;
               return;
           }
           cur = cur.next;
       }
       System.out.println("没有找到该关键字!");*/

       ListNode cur = searchPerv(key);
       if (cur == null){
           System.out.println("没有你要删除的节点!");
           return;
       }
       ListNode del = cur.next;
       cur.next = del.next;

   };

   //删除所有值为key的节点 ( 要求遍历链表一遍,删除所有为key的值 )
   public void removeAllKey(int key){
       if (this.head == null){
           System.out.println("单链表为空,不能删除!");
           return;
       }
        ListNode cur = this.head.next;
        ListNode pre = this.head;
        while (cur != null){
            if (cur.val == key){
                pre.next = cur.next;
                cur = cur.next;
            }else {
                pre = cur;
                cur = cur.next;
            }
        }
        //最后处理头
        if (this.head.val == key){
            this.head = this.head.next;
        }
   };

   public void clear(){
       //this.head = null 比较粗暴的做法,最好还是挨个置null
       while (this.head != null){
           ListNode curNext = this.head.next;
           this.head.next = null;
           this.head = curNext;
       }
   };

}
